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(11) | EP 0 961 009 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Conjugate screw rotor profile |
| (57) The point of tangency of the tip circle (TM) of the male rotor (16) and the root circle (TF) of the female rotor (14) is used as a starting point in generating the series of
curves defining the male and female conjugate rotor profiles. The present invention
provides: reduced viscous drag through the use of a departure angle (Δ1,Δ2); strengthened female lobes (14-1) by controlling thickness along the pitch circle
(PF); opened root of male rotor (16) to enhance manufacturability and tool life; a tortuous
leakage path for gas traveling from a high pressure thread to a low pressure thread;
better control of root diameter; and control of the pressure angle independently of
the other variables. |